Mercedes A class AMG v BRZ?

[Dephective]

Small turbo=faster spool=high torque stress on rods,pistons,etc.

Large turbo=slower spool=torque band spread out=linear stressing on said components.

If you yank on something, you are liable to break it. But if you gradually apply force, the forces that the object can withstand becomes greater, because there is less peak stress.

This is a crude way to explain it and shouldn't be taken literally. You can also do things like tune boost by RPM and have a gradual increase in PSI over the RPM range which would relieve a lot of stress off the internals as well. This concept has been applied for years in the tuner scene, but requires an EBCS

OEM manufacturers want gobs of low-end torque because of stringent emissions and fuel economy standards, which is why they go low displacement, small turbos that spool ridiculously quick. For this you need components that handle the high stresses that they will see. It's actually very difficult to size a turbo right, there are whole third party companies that specify in this field.

[fatoni]

Originally Posted by Dephective

Small turbo=faster spool=high torque stress on rods,pistons,etc.

Large turbo=slower spool=torque band spread out=linear stressing on said components.

If you yank on something, you are liable to break it. But if you gradually apply force, the forces that the object can withstand becomes greater, because there is less peak stress.

This is a crude way to explain it and shouldn't be taken literally. You can also do things like tune boost by RPM and have a gradual increase in PSI over the RPM range which would relieve a lot of stress off the internals as well. This concept has been applied for years in the tuner scene, but requires an EBCS

OEM manufacturers want gobs of low-end torque because of stringent emissions and fuel economy standards, which is why they go low displacement, small turbos that spool ridiculously quick. For this you need components that handle the high stresses that they will see. It's actually very difficult to size a turbo right, there are whole third party companies that specify in this field.

this is where the correlation stops making sense to me. i cant see the speed of the turbo having any direct effect on internals. i can see how a larger turbo will spin slower than a small turbo at any give pressure. what i dont understand is how a small turbo at any given boost pressure is more damaging than a large turbo at the exact same pressure.

torque over time is hp and i dont think hp is what breaks motors. i think in this example, torque needs to be looked at an instance. if it takes x tq to break a con rod, i dont think it matters how long it takes the engine to make x amount of tq or how smooth it gets there.

[atledreier]

Passed one A45AMG on my tight track with a stock GT86. I was on R888, he was on P Zeros. We both had a passenger. He was pushing WAY hard to keep me behind, almost ran off the track a few times. When I passed him he went into the pits claiming to have to cool the brakes. I pitted for another passenger and went out again. Next time I met him he claimed his gearbox overheated... I drove 3 hours more or less non stop, no issues. He was in every 6 laps cooling something... Pretty quick in a straight line though.

[chrisl]

Originally Posted by gt8613

The FA20 is arguably the best boxer motor to date. Check out Crawford's review.

Best Subaru boxer, maybe, but not the best boxer motor. I'd take the engine out of a GT3, 911 Turbo S, or GT2 any day over the FA20.

[WolfpackS2k]

Originally Posted by InvalidJohnny5

But do we really want Mercedes dependability?

A hand built Mercedes AMG engine with forged internals or a mass produced Subaru engine with cast internals.

Yeah I'll take the Merc.

But these cars aren't even close to competitors so this comparison is silly. Still, the CLA AMG is a LOT of car for $45k. Really puts the Evo and STI to shame.

[czar07]

Originally Posted by Dephective

Small turbo=faster spool=high torque stress on rods,pistons,etc.

Large turbo=slower spool=torque band spread out=linear stressing on said components.

If you yank on something, you are liable to break it. But if you gradually apply force, the forces that the object can withstand becomes greater, because there is less peak stress.

This is a crude way to explain it and shouldn't be taken literally. You can also do things like tune boost by RPM and have a gradual increase in PSI over the RPM range which would relieve a lot of stress off the internals as well. This concept has been applied for years in the tuner scene, but requires an EBCS

OEM manufacturers want gobs of low-end torque because of stringent emissions and fuel economy standards, which is why they go low displacement, small turbos that spool ridiculously quick. For this you need components that handle the high stresses that they will see. It's actually very difficult to size a turbo right, there are whole third party companies that specify in this field.

Mate have you ever driven a big turbo? Spread out torque band? are you high?

And LOL @ audi quality..yeah k..

[Dephective]

Originally Posted by czar07

Mate have you ever driven a big turbo? Spread out torque band? are you high?

And LOL @ audi quality..yeah k..

I didn't mean spread out the torque band in a sense that you have more of it, yet your power and is smaller with a bigger turbo. that was poor communication on my part. I had a BT rx7 FD. I was basically referring to lag making the torque less immediate

@fatoni
I am not an engineer, so I cannot explain it better than anecdotal evidence, but Evo and MS3 guys pushing crazy numbers on stock block have applied this concept quite frequently.


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